DE959364C - Device for carrying out endothermic gas reactions - Google Patents

Description

In chemical processes in which at least one reaction partner is in a gaseous state and the reaction can be initiated or maintained by the indirect supply of heat must, the design of the reaction space is a particularly difficult problem. this especially applies when it comes to implementations whose course through the common ones Materials normally preferred because of their good heat transfer properties used in such cases is disturbed. Such difficulties are for example before if the pipe material reacts with the used catalyst or poisons it or if the starting materials of the reactions or the reaction product by the material of the Reaction vessel catalytically influenced, for example decomposed, are. Also the lack of temperature resistance metallic materials can play a role as a hindrance to carrying out the reaction described.

For these reasons, the use of ceramic materials has already been considered drawn, since these are disadvantageous as a material for reaction vessels, in particular reaction tubes Properties of the metals do not show, but on the other hand because of their thermal sensitivity fail easily when the task is set, in the interests of high throughput to create large, technically usable equipment. In addition, you have ceramic tubes cannot produce in any large dimensions due to their specific production method or but at least not in such a way that they thermally meet the requirements of a rough technical operation and would have grown in terms of strength.

For this reason, a large number of tubes have also been used for technical equipment of smaller dimensions, which are essential against thermal and mechanical stresses are more resistant to combine to form larger units with a satisfactory throughput and In this way he got to furnaces which had a bundle of a multitude of ceramic in a boiler room Tubes included. The prerequisite for ίο technical usability is that the pipes so in The heating devices are built in that they withstand thermal stresses and other mechanical Dodge or pursue stress, so that not every extraordinary stress a destruction of at least one pipe and thus possibly the failure of the entire unit evokes.

Furnaces with ceramic tubes are known in which the tubes move more or less freely are suspended in the end walls of the actual furnace body, the sealing of the Oven front wall by cut plates or the like pushed over the pipes.

In the case of devices that consist of a large number of individual units, in the present case of pipes, are constructed, it is particularly important for trouble-free operation to treat each pipe individually, can be loaded or emptied and removed from the oven at will without the work of the other pipes is disturbed and the reaction products formed in these pipes are contaminated will.

This object is based on the invention, which provides a device for performing endothermic, relates in particular to catalytic gas reactions in reaction tubes made of ceramic material. There are already known tube furnaces with metallic reaction tubes, which are supported by jacket tubes are protected and where there is the possibility of treating each pipe individually without that the reaction process is disturbed in the other tubes. But such ovens also show the disadvantages of metallic materials already mentioned at the beginning. Besides, the construction a furnace made of ceramic material is much more difficult because of its inelastic behavior and therefore not without further ado with the construction of a tubular furnace made of metallic material to compare.

In the device according to the invention, the reaction tubes can be made of ceramic material be used individually or in groups in a boiler room so that they can move freely is retained even under thermal stress and therefore the occurrence of harmful Tensile or shear stresses during temperature changes are avoided. Even with one of a large number of pipes existing technical aggregate can the individual pipes under special conditions operate.

In the device according to the invention, the ceramic reaction tubes are in corresponding Channels of a cooling head used gas-tight, this cooling head not expediently at the same time only the cooling of the tube ends or the gases leaving the reaction tubes, but also the gas evacuation itself is used. At the free end, each reaction tube is connected to a control head, the one in a guide body communicating with the reaction tube and closable to the outside Bore carries. The clear width of this bore should exceed that of the reaction tube, so that it may be possible to remove the reaction tube to the outside through this bore. This hole in the guide body also serves to supply gas to the reaction tube and is for this purpose in connection with the plenum of the gas distributor, for example by lockable Channels that are provided with valves or similar devices. The entire device can be made with the gas distributor at the top and the cooling head at the bottom the reaction tubes is located. Preferably, however, the reaction tubes are in the channels of the cooling head is suspended, so this is arranged on the top and the lower end of the pipe brought into communication via a flexible connection with the control head.

A device according to the invention is shown schematically in FIG. 1 as an example of an embodiment. The device consists of a plurality of reaction tubes labeled 1, from the cooling head 2 with the channels which are present for each individual pipe and are surrounded by cooling spaces 3 and the cover 4. The lower end of the device is formed by the gas distributor 5, which in turn again the control head 6 with the guide body 7 and the control sleeve 8 and the closure cover 9 wearing.

As can be seen from the figure, the cooling head 2 can advantageously be made in several parts and from a lower piece 10, a middle piece 11 and the top piece 4 'which at the same time forms the cover. The end faces of all Cooling head parts are machined smooth, so that they lie tightly on top of each other and through appropriate Packs, e.g. B. in the grooves 12, are to be combined in a gas-tight manner. The fastening of the cooling head parts with one another can take place in a manner known per se; in the drawing are clamping lever locks for this purpose 13 provided.

In the case of the split cooling head, the upper ends of the reaction tubes 1 are inserted into the cooling head lower part 10 inserted so that they are approximately flush with the top edge of 10. On the floor of the lower part are, for example with the help of studs, pierced heads 14 from a Metal with good thermal conductivity, advantageously made of copper, put on as a receptacle for the Serve pipe ends. Between the pipe ends and iao the copper heads 14 is a temperature-resistant Inserted pack, which can for example consist of asbestos rings 15, the top and bottom held with ceramic rings 16 and pressed together with a threaded ring 17. To this Way is a gas-tight seal of the pipe end

reached against the cooling head spaces, which only then removed by removing the middle and upper piece needs to be when the tube needs to be replaced. The copper head 14 enables a rapid dissipation of the heat from the pipe end and transfer of this heat to the actual one Cooling surfaces of the cooling head.

In the embodiment shown, there are still on the lower piece 10 of the cooling head 2 the rail-like extensions 18, which are used to support the entire device in any Serve oven. To avoid excessive thermal and mechanical stress on the hanging in the furnace To avoid the device, the support part of the furnace surrounding the device is expedient chosen so that it is without connection with thermally variable furnace parts. The oven itself can be used in any way, e.g. electrically, but also - this method of working is preferable - be heated with gas.

The connection of the reaction tube 1 to the gas distributor 5 is expediently carried out via the Light metal tube 19, with which it is firmly connected at 20, for example by a putty.

Essential for the usefulness of the entire device is the fact that, as can also be seen from the figure, this metal tube 19, which is the continuation of the reaction tube, is immersed in the channel of the guide body 7 _{with a large margin and therefore freely movable in all directions at 20 a.} The gas-tight connection between the guide body and the intermediate metal piece is produced by a flexible cover 21, which can consist of rubber, silicone rubber or other plastic, impermeable materials.

The distributor 5 carries the common gas supply line, not visible in the figure, from which the gas can pass into the bore γ _{α of} the guide body via channels 22 located in the guide body 7, which expediently run out into nozzle-like openings. In the device according to the invention, the gas is supplied together, but then separately allocated to each individual guide body and thus to each individual reaction tube by means of the channels mentioned from the common gas space. As mentioned, the guide body 7 carries the control sleeve 8, which acts similarly to a union nut. It is sealed against the guide body with the aid of the screw ring 23 and the packing 24 and can be adjusted upwards or downwards by turning the thread 25. If during this actuation the control sleeve 8 is turned upwards in relation to the position shown in the figure! so the annular, elastic packing 26 is compressed and closes the channels 22 of the guide body 7 so that no gas can pass from the distributor into the bore J _{a of} the guide body and thus into the reaction tube. In this way it is possible to shut off each individual reaction tube of the device from the general gas supply during operation from the outside. In addition, this device now also allows the tube, which is separated from the general gas supply, to be opened via the closure cover 9 without again disrupting the overall operation of the other reaction tubes. For example, a broken pipe can be pulled downward out of the device through this opening and a fragment can be removed. Much more important, however, is that here z. B. can use a pressure gauge for individual measurements or provide check valves for the individual introduction of other gases. Such measurements or charging with other gases can be carried out in each individual tube for any length of time, while the other tubes continue to work without interference.

In a similar way, packing elements or in the reaction tube during operation are introduced from individual pieces of existing packing columns, which are then placed after the Shutter cover 9 rest on this and do not stress the sensitive reaction tube. Also the Replacing this packing can after switching off the gas supply by actuating the Control sleeve 8 and loosening of the closure cover made during the operation of the other tubes will.

The possibility of an individual gas supply for individual or all pipes provided by the configuration according to the invention proves to be a great advantage when supplying preheated gases or gas mixtures, the gas distributor 5 and the flexible connections not being allowed to heat up excessively. It is advisable to proceed in such a way that separate tubes are passed through the sealing cover 9 for the hot gas, which tubes extend into the actual ceramic reaction tube without impairing its freedom of movement (see FIG. 2). At the same time, through the channels 22 of the guide body 7, under regulation by means of the control sleeve 8, cold gas or gas mixture is introduced in such a way that its pressure is sufficient to prevent the hot gas from blowing back from the reaction tube into the wide channel J _{11 of} the guide body 7 and the connecting tube 19 between to prevent this and the reaction tube.

A preferred embodiment of the device according to the invention, which allows the advantages of the construction of distributor 5 and control head 6 for the individual application of the pipes in a particularly exhaustive manner, consists in that in the cover 4 or in the upper part of the cooling head 2 pipe sockets are used, which can be closed to the outside by taps fitted on T-pieces, if necessary, and each of them a reaction tube or a corresponding channel in the cooling head 2 or in the middle piece 11 iao assigned. These pipe sockets, which are designated in Fig. Ι with 27, are threaded provided and accordingly lowerable in the lid. They are at the bottom with divider-like Sealing elements 28 are provided, which in the lowest position of the pipe socket 27 are in disk-shaped

Insert shaped recesses 29 at the end of the channels 3 of the middle piece ii and rest in these as it were as valve seats. This embodiment makes it possible to complete each individual channel 3 or each individual reaction tube by lowering the associated pipe socket 27 from the common gas space in the upper part of the cooling head and thus discharge the gases separately from the tube in question. By lifting the pipe socket 2.7 , the channel in question opens again into the common gas space. With the help of this design, the exhaust gases of each individual pipe can be fed to the gas analysis or, for example, a temperature measuring instrument, for example a thermocouple, can be inserted into the T-piece that forms the end of the pipe socket 27 to the outside, in order to monitor the course of the reaction in a single pipe without Disturbance of the operation of the other reaction tubes based on the reaction temperature

ao ratur to follow.

In Fig. 2, the lower part of the device is shown again separately in order to explain the additional device for preheating the reacting gases. The meaning of the reference numerals 1, 7, "] _a , 8, 9, 19, 20, 20 _a and 21 to 20 - corresponds to that in FIG consists of a material with high thermal conductivity, preferably copper. The preheating of the gas introduced through 30 is carried out by a heating device 31. By setting the control sleeve 8 accordingly, the collecting space of the gas distributor 5 (FIG. 1) becomes so much via the channels 22 cold gas is introduced so that it forms a cooling cushion surrounding the tube 30 in the bore j _{a of} the guide body 7, within the flexible sleeve 21 and in the tube 19. In this way, undesired heating of the connection points and seals is avoided without the relatively slight The amount of cold gas causes a significant loss of heat from the preheated gas Separate strongly preheat and, if necessary, combine the gas inlet pipes 30, the closure cover 9 and the heating devices 31 into a separate structural part.

The device according to the invention is generally used to carry out endothermic, in particular catalytic gas reactions, e.g. B. for the hydrogen cyanide synthesis from methane and ammonia, for the Wulff process for the production of acetylene from methane or other saturated, lower ones Hydrocarbons, for the cracking and formation of gasified crude oil and the like Catalyst as a coating on the wall of the reaction tube or on through the closure lid 9 supported packing can be applied. You can also make the packing yourself Produce catalytically active material and, as described above, in each individual tube Replace or check during operation by removing the pipe in question from the general Gas supply is temporarily shut off.

Proven particularly useful apparatus of the invention for the preparation of hydrogen cyanide from methane and ammonia over a catalyst of the platinum group, which is carried out at temperatures of about 1200 ⁰ Pursuant. The device according to the invention has proven to be particularly useful in processes of this type, in which the catalyst in individual reaction tubes may occasionally need to be regenerated, because it allows any work that may arise on the individual tube to be carried out without operation interrupting or disrupting the other pipes and contaminating the resulting reaction products. It is Z. B. ohrje further possible, by closing the gas channels 22 in the guide body 7 with the help of the control sleeve 8 the pipe after removing the cap 9 any gases, ζ. B. oxygen or air, and in this way by-products such. B. soot deposits to be removed by burning off from the reaction tube. A contamination of the jointly discharged reaction product of the other pipes does not occur, since the pipe in question is separated from the general gas discharge with the help of the pipe socket 27, so that the corresponding gases can either be discharged by themselves or, for example, burned off at the pipe socket on the outside.

Another advantage of using the device of the invention also results from the fact that that it is possible, if necessary, to use individual pipes with gas mixtures of different compositions to be charged and so adapt the individual reaction to the state of the catalyst. By setting different opening cross-sections on the channels 22 of the guide body 7 can an application with different amounts of gas can be achieved.

In the production of hydrocyanic acid from methane and ammonia, that described in accordance with FIG. 2 can be used The possibility of preheating the reaction components can be of great importance. You can do that process that approximately only the ammonia is preheated to temperatures of 700 to 8oo ° and additionally cold methane-ammonia mixture is introduced via the channels 22. As particularly beneficial However, it has proven to preheat the mixture of ammonia and methane, since the losses due to premature decomposition are surprisingly lowest here.

Claims (5)

PATENT CLAIMS: i. Device for carrying out endothermic gas reactions, especially catalytically effective surfaces, consisting of a plurality of reaction tubes made of ceramic material that can be inserted into a heating room, which is attached gas-tight at one end and elastic at the other end with a gas distributor are connected, characterized in that the reaction tubes (i) in corresponding channels (3) a cooling head (2) which simultaneously serves to discharge the gases together in a gastight manner inserted, preferably suspended, and a gas distributor (5; for each pipe with a control head (6) is provided, which is in a guide body (7) a central, with the corresponding End of the reaction tube communicating and closable to the outside bore (7a) carries the inside diameter of the outer diameter of the associated reaction tube and which can be shut off via channels (22) in the guide body (7) is connected to the collecting space of the gas distributor (5). 2. Device according to claim i, characterized in that that on the part of the guide body (7) facing away from the gas distributor (5) there is a control sleeve provided with a removable cover (9) (8) in the manner of a screw cap, rotatably mounted on an annular support an elastic sealing element (26) carries which, when the control sleeve is rotated accordingly (8) the, expediently in nozzle-like opening. expiring, gas channels (22) of the guide body (7) blocks gas-tight against the central bore of this body or for gas passage releases. 3. Apparatus according to claim 1 and 2, characterized in that through the cover (9) and the central bore (7 ₀ ) of the guide body (7) separate gas inlet tubes (30) extending into the reaction tube (1) are guided. 4 · Device according to claim 1 to 3, characterized characterized in that the cooling head (2) consists of several parts, preferably three parts and the lower part (10) is approximately flush with the upper edge of the upper part inserted into it Ends the pipe ends by a heat-resistant, elastic packing (15) in with the Lower part (10) permanently connected heads (14) made of a metallic material with good Thermal conductivity, advantageously copper, are held, while the central part (11) of Has channels (3) which are surrounded by cooling spaces and communicate with the reaction tubes, those in the collecting space of the upper part (4) connected to the common gas discharge flow out. 5. Device according to one of claims 1 to 4, characterized in that in the Lid (4) of the cooling head (2) pipe socket (27) which can be closed to the outside and can be lowered, Are expediently screwed in, one of which each with a reaction tube communicates, and attached to the lower end plate-like sealing elements (28) are in the lowest position of the pipe socket (27) in disc-shaped recesses (29) rest at the upper end of the channels (3) of the central part (11) as a valve seat and the associated Reaction tube from the gas collection space located in the cooling head and the common gas discharge line connected to it to lock. Considered publications:
German patent specifications No. 855242, 884348. 1 sheet of drawings © 609617/472 8.56 (609 833 2.57}